1. Understanding Cancer and Related Topics
Developed by: Lewis J. Kleinsmith, Ph.D. Donna Kerrigan, M.S. Jeanne Kelly Brian Hollen
Discusses and illustrates what cancer is, explains the link between genes and cancer, and discusses what is known about the causes, detection, and diagnosis of the disease.
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2. Understanding Cancer and Related Topics
What Is Cancer?
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Cancer is a renegade system of growth that originates within a patient’s biosystem, more commonly known as the human body. There are many different types of cancers, but all share one hallmark characteristic: unchecked growth that progresses toward limitless expansion.
It is difficult to imagine anyone who has not heard of this illness. Most people have been affected because either they or their loved ones or friends are cancer survivors.
Because cancer is so prevalent, people have many questions about its biology, detection, diagnosis, possible causes, and strategies for prevention.
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3. Different Kinds of Cancer Understanding Cancer and Related Topics
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Leukemias:
Bloodstream
Some common carcinomas:
Lung
Breast (women)
Colon
Bladder
Prostate (men)
Lymphomas:
Lymph nodes
Some common sarcomas:
Fat
Bone
Muscle
Cancer can originate almost anywhere in the body.
Carcinomas, the most common types of cancer, arise from the cells that cover external and internal body surfaces. Lung, breast, and colon are the most frequent cancers of this type in the United States.
Sarcomas are cancers arising from cells found in the supporting tissues of the body such as bone, cartilage, fat, connective tissue, and muscle.
Lymphomas are cancers that arise in the lymph nodes and tissues of the body’s immune system.
Leukemias are cancers of the immature blood cells that grow in the bone marrow and tend to accumulate in large numbers in the bloodstream.
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4. Understanding Cancer and Related Topics
Naming Cancers
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Cancer Prefixes Point to Location
Prefix Meaning
adeno- gland
chondro- cartilage
erythro- red blood cell
hemangio- blood vessels
hepato- liver
lipo- fat
lympho- lymphocyte
melano- pigment cell
myelo- bone marrow
myo- muscle
osteo- bone
Scientists use a variety of technical names to distinguish the many different types of carcinomas, sarcomas, lymphomas, and leukemias. In general, these names are created by using different Latin prefixes that stand for the location where the cancer began its unchecked growth. For example, the prefix “osteo” means bone, so a cancer arising in bone is called an osteosarcoma. Similarly, the prefix “adeno” means gland, so a cancer of gland cells is called adenocarcinoma-- for example, a breast adenocarcinoma.
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5. Loss of Normal Growth Control
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Normal cell division
Cell Suicide or Apoptosis
Cell damage— no repair
Cancer cell division
Cancer arises from a loss of normal growth control. In normal tissues, the rates of new cell growth and old cell death are kept in balance. In cancer, this balance is disrupted. This disruption can result from uncontrolled cell growth or loss of a cell’s ability to undergo cell suicide by a process called“apoptosis.” Apoptosis, or “cell suicide,” is the mechanism by which old or damaged cells normally self-destruct.
First mutation
Second mutation
Third mutation
Fourth or later mutation
Uncontrolled growth
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6. Example of Normal Growth Understanding Cancer and Related Topics
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Dead cells shed from outer surface
Epidermis
Cell migration
Dividing cells in basal layer
Dermis
To illustrate what is meant by normal growth control, consider the skin. The thin outermost layer of normal skin, called the epidermis, is roughly a dozen cells thick. Cells in the bottom row of this layer, called the basal layer, divide just fast enough to replenish cells that are continually being shed from the surface of the skin. Each time one of these basal cells divides, it produces two cells. One remains in the basal layer and retains the capacity to divide. The other migrates out of the basal layer and loses the capacity to divide. The number of dividing cells in the basal layer, therefore, stays the same.
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7. The Beginning of Cancerous Growth
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Understanding Cancer and Related Topics
Understanding Cancer
During the development of skin cancer, the normal balance between cell division and cell loss is disrupted. The basal cells now divide faster than is needed to replenish the cells being shed from the surface of the skin. Each time one of these basal cells divides, the two newly formed cells will often retain the capacity to divide, thereby leading to an increase in the total number of dividing cells.
Underlying tissue
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8. Understanding Cancer and Related Topics
Tumors (Neoplasms)
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
This gradual increase in the number of dividing cells creates a growing mass of tissue called a “tumor” or “neoplasm.” If the rate of cell division is relatively rapid, and no “suicide” signals are in place to trigger cell death, the tumor will grow quickly in size; if the cells divide more slowly, tumor growth will be slower. But regardless of the growth rate, tumors ultimately increase in size because new cells are being produced in greater numbers than needed. As more and more of these dividing cells accumulate, the normal organization of the tissue gradually becomes disrupted.
Underlying tissue
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9. Invasion and Metastasis Understanding Cancer and Related Topics
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer 1
Cancer cells invade surrounding tissues and blood vessels 2
Cancer cells are transported by the circulatory system to distant sites
Cancers are capable of spreading throughout the body by two mechanisms: invasion and metastasis. Invasion refers to the direct migration and penetration by cancer cells into neighboring tissues. Metastasis refers to the ability of cancer cells to penetrate into lymphatic and blood vessels, circulate through the bloodstream, and then invade normal tissues elsewhere in the body. 3
Cancer cells reinvade and grow at new location
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10. Malignant versus Benign Tumors Understanding Cancer and Related Topics
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Benign (not cancer) tumor cells grow only locally and cannot spread by invasion or metastasis
Malignant (cancer) cells invade neighboring tissues, enter blood vessels, and metastasize to different sites
Depending on whether or not they can spread by invasion and metastasis, tumors are classified as being either benign or malignant. Benign tumors are tumors that cannot spread by invasion or metastasis; hence, they only grow locally. Malignant tumors are tumors that are capable of spreading by invasion and metastasis. By definition, the term “cancer” applies only to malignant tumors.
Time
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11. Why Cancer Is Potentially Dangerous
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Brain
Melanoma cells travel through bloodstream
Liver
Melanoma (initial tumor)
A malignant tumor, a “cancer,” is a more serious health problem than a benign tumor because cancer cells can spread to distant parts of the body. For example, a melanoma (a cancer of pigmented cells) arising in the skin can have cells that enter the bloodstream and spread to distant organs such as the liver or brain. Cancer cells in the liver would be called metastatic melanoma, not liver cancer. Metastases share the name of the original (“primary”) tumor. Melanoma cells growing in the brain or liver can disrupt the functions of these vital organs and so are potentially life threatening.
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